Trials of Hypertension Prevention (TOHP) is a three-phase collaboration involving randomized clinical trials to determine if non-pharmacologic interventions can prevent increases in blood pressure leading to systemic hypertension. TOHP was developed as a collaborative agreement by the NHLBI. Phase I of TOHP was a 3-year feasibility trial designed to test the short term effectiveness of severe non-pharmacologic interventions in reducing or preventing an increase in rise in diastolic blood pressure (DBP). Phase II, as conceived by NHLBI, will be a 5-year trial to test the effectiveness of the interventions determined to be most effective in Phase I in preventing the onset of definite hypertension. Phase III will be a period for data analysis and reporting of results. Nine of 10 clinical centers participating in Phase I, a coordinating center, central laboratory, and nutrient data center propose to continue in Phase II. Specifically, this phase will test whether the combination of weight loss and dietary sodium restriction or weight loss alone will decrease the incidence of definite hypertension in 2,250 individuals, aged 30 to 54 years, with high normal DBP. In addition, the trial will compare the effects of weight loss and sodium restriction combined and weight loss alone on change in DBP. Recruitment will be divided equally between clinics. The major eligibility criteria will be DBP (83-89 mmHg) and weight (110-160% of ideal body weight). Within each clinic, participant will be randomized to either of the two active treatment groups or a no- treatment control. Follow-up will be for 36 months for the incidence of hypertension. Data for change in blood pressure will continue to be collected for an average of 42 and maximum of 48 months follow-up. The study is designed to provide 90% power to determine a 40% reduction in the incidence of definite hypertension with the combined intervention and a 30% reduction in incidence with weight loss alone. The study also has 90% power to detect a 1.5 mmHg change in diastolic blood pressure between the two active treatment groups.